First you need to set up your categories within the Administrator>Virtual Web Application Manager portlet. Then to add the Web Dock portlet to a page, you need to go to Administrator>Manage pages. From there, you can create a new page or locate an existing page. Click the Edit Page Layout icon. You'll get a page where you can add portlets. Click the plus button (Add portlets). You'll have a list of portlets that you can select to add to the page. I found the Web Dock portlet on page 8 of 9. I hope that helps.
You may also need to set the Page Properties > Theme Settings to the Portal 8.0 Theme and a Full profile.
You may also need to set the Page Properties > Theme Settings to the Portal 8.0 Theme and a Full profile.